1. Field of Invention
The present invention relates to an integration system and the method for operating the same. More particularly, the present invention relates to an integration system for integrating and managing a plurality of photolithography tools and the method for operating the same.
2. Description of Related Art
In the manufacture of integrated circuits, photolithography is used to transfer patterns from a photo mask having customized circuit patterns to thin films formed on a wafer. The image transfer process comprises steps of forming a photoresist layer on a non-process layer, illuminating the photoresist layer through a photo mask having the customized circuit patterns, developing the photoresist layer and then etching the non-process layer by using the patterned photoresist layer as a mask. Hence, the image transfer process is accomplished. For a well-manufactured integrated circuit product, the image transfer process mentioned above is performed several times to transfer the circuit patterns to each non-process layer to form the electrical device. Therefore, it is important to align the successive patterned layers to reduce the misalignment errors as the critical dimension of the semiconductor device becomes smaller and smaller.
Typically, before the exposure process is performed to transfer the patterns on the photo mask to the photoresist layer formed on the wafer, an alignment process is performed to align the alignment mark on the photo mask to the alignment mark on the wafer. Meanwhile, a test wafer is used to determine the overlay offset parameters and the exposure dose for a particular photolithography process on a particular photolithography tool. The overlay offset parameters are used to ensure the alignment precision between the successive patterned layers and the exposure dose is used to precisely control the critical dimension of the formed layer. However, the process for measuring the overlay offset parameters and the exposure dose by using a test wafer will increase the manufacturing cost and lower down the throughput. Therefore, a photo feedback system is developed to collect the metrology parameters after the exposure and develop process is performed for obtaining a set of overlay offset parameters and then the obtained overlay offset parameters are stored in the host terminal in a way corresponding to the recipe parameters for forming the process layer on the particular photolithography tool. By using the historical overlay offset parameters, the cost for using the test wafer for measuring the overlay offset parameters and the exposure dose can be saved.
Nevertheless, the typical photo feedback system is a tool-centered system focusing on collecting metrology parameters for the photolithography tools respectively. Even though using the same formation recipe to form the same process layer, the different photolithography tools will lead to different sets of overlay offset parameters for the same process layer. For a semiconductor factory with various and mass production lines, many photolithography tools are in use simultaneously. Hence, if a mask is going to be used in a photolithography tool but there is no record about the mask in the photo feedback system of the tool, it is inevitable to use a test wafer to perform a test run which is also known as send-ahead process to determine the overlay offset parameters and the exposure dose even though the mask is used in the other photolithography tool before. Moreover, since even the same preceding process layers which are from in different photolithography tools (the photolithography tool used to form the preceding process layer is denoted as pre-tool in the following description) lead to different metrology results, it is also foreseeable to use a test wafer to performed a test run in order to determine the overlay offset parameters and the exposure dose when the preceding process layer is formed in a photolithography tool, which the preceding process layers for the historical process are not ordinarily formed in and no record of these overlay offset parameters is found in the photo feedback system of. That is, the overlay offset parameters are not efficiently managed and integrated in the current tool-centered photo feedback system. Furthermore, under the circumstances mentioned above, the time for performing the test run and for obtaining metrology result of the test wafer after the test run seriously affect the manufacturing cost and throughput.